In the reaction between hydrogen selenide (H₂Se) and water, H₂Se acts as the acid, donating a proton (H⁺) to water. Water (H₂O) functions as the base, accepting the proton to form the hydronium ion (H₃O⁺). The conjugate acid formed in this reaction is H₃O⁺, which is the product of water after gaining a proton. The conjugate base is SeH⁻, which results from H₂Se losing a proton.
In this context, H₂Se is a weak acid, and its behavior as such can be explained by the presence of selenium (Se), a nonmetal that, like sulfur (S) and oxygen (O), can participate in proton donation due to its electronegativity and ability to stabilize the negative charge on SeH⁻ after losing a proton. Water, being a polar molecule, has the capability to act as a base by accepting protons due to the presence of lone pairs on the oxygen atom.